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A Quick Tutorial on AMD64

AMD64 is the term used by AMD to describe its 64-bit extensions to the 32-bit x86 architecture used by Intel processors since the 386 and by AMD processors since the K5 and K6. Because AMD64 is based on x86 architecture, processors using the AMD64 architecture such as the Athlon 64 family, the AMD Turion 64 mobile technology platform, and the AMD Opteron family of server and workstation processors can use 64-bit operating systems to handle larger amounts of memory and disk space than those accessible with a 32-bit operating system. However, unlike the EPIC architecture used by Intel's Itanium family of enterprise server-class processors, AMD64 can run existing 32-bit operating systems and applications at full speed without translation layers or software helpers.

Athlon 64 FX Form Factors and Models

Originally, the Athlon 64 FX, which uses an integrated dual-channel memory controller for greater speed than the desktop or mobile Athlon 64 series, used the same 940-pin socket as the AMD Opteron, AMD's AMD64-based server and workstation processor family. Athlon 64 FX processors using the 940-pin socket must also use the same expensive registered DDR DIMM memory as the Opteron.

Currently, most Athlon 64 FX processors use Socket 939, which supports the same unbuffered DDR DIMM memory that the Athlon 64 and other current desktop processors use.

The Athlon 64 FX family includes three models as shown in Table 1. The FX-51 (shaded row) is now discontinued.

Table 1 – AMD Athlon 64 FX Processor Models

Processor Model

Clock Speed

939-pin Socket

940-pin Socket

FX-51

2.2GHz

No

Yes

FX-53

2.4GHz

Yes

Yes

FX-55

2.6GHz

Yes

No

As you can see from Table 1, the FX-53 has been produced in both the non-obsolescent Socket 940 form factor and the current Socket 939 form factor. How can you make sure you are getting the correct processor form factor? Figure 1 compares the OPNs (part numbers) for a Socket 939 part and a Socket 940 part.

Figure 1

Figure 1 The OPN for a Socket 940 part has a C after FX53, while a Socket 939 part has a D in this location. Look for the "D" parts if you have a Socket 939 motherboard.

Athlon 64 Desktop Form Factors and Models

Originally, the Athlon 64, which uses an integrated single-channel memory controller, used Socket 754. However, recent versions of this processor, including the fastest versions, use Socket 939 and incorporate a dual-channel memory controller, just as the latest versions of the Athlon 64 FX processor do. Versions in both form factors might use 512KB or 1024KB (1MB) of L2 cache, as shown in Table 2. Note that Socket 939 also supports the faster 1GHz HyperTransport pathway between chipset components.

Table 2 – AMD Athlon 64 Processor Models

Processor Model

Clock Speed

Socket Type

L2 Cache Size

HyperTransport Speed

Integrated Memory Controller

2800+

1.8GHz

754

512KB

800MHz

64-bit

3000+

2.0GHz

754

512KB

800MHz

64-bit

3200+

2.0GHz

754

1024KB

800MHz

64-bit

3200+

2.2GHz

754

512KB

800MHz

64-bit

3400+

2.2GHz

754

1024KB

800MHz

64-bit

3400+

2.4GHz

754

512KB

800MHz

64-bit

3500+

2.2GHz

939

512KB

1GHz

128-bit

3700+

2.4GHz

754

1024KB

800MHz

64-bit

3800+

2.4GHz

939

512KB

1GHz

128-bit

4000+

2.4GHz

939

1024KB

1GHz

128-bit

Unlike the Athlon 64 FX, in which processors with the same basic model number are available in two different form factors, the Athlon 64 uses different model numbers for the older Socket 754 and newer Socket 939 parts.

As you can see from Table 2, Socket 939 models (3500+, 3800+, and 4000+) are better choices than Socket 754 models because they include a dual-channel memory controller and faster HyperTransport performance. Dual-channel memory controllers provide faster performance because they access a pair of matched memory modules (same size, speed, and latency) as a single unit. The faster performance that dual-channel memory and the faster chipset connection offer is the reason for the improved rating model numbers in the 3800+ and 4000+ versus the 3700+, all of which run at 2.4GHz.

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